High Impact PolyStyrene (HIPS) is a frequently used filament in 3D printing. It has been touted to have simular properties when printed to ABS and is especially useful for support structures (if the user has a multi-nozzle 3d Printer) as it is soluble in Limonene.
General Purpose PolyStyrene (GPPS) is frequently used in disposible cups, cutlery, etc. I don't believe I have seen it as a 3D printing filament. This is not styrofoam for the purpose of this question despite the identical chemical properties as the incorperated air makes it difficult to recycle.
Would filament produced from GPPS, be usable on most FFF 3D printers that are capable of using ABS, PLA, and HIPS? Are that any particular issues observed with such filaments that would not be observed with HIPS (besides the implied decrease in impact resistance)?
Note: For the purpose of this question, I am assuming that the filament can be produced and am concerned about whether the filament would be usable for support structures and infill.
In principle, it should work fine as a filament, since it's used extensively in the plastic extrusion industry, but I don't think you'd get great material properties out of it. ABS and HIPS incorporate polybutadiene into a graft polymer structure for a very good reason: the butadiene sections in the long molecular chains kind of "stick together" as a distinct solid phase to produce what amounts to micro-bubbles of rubber inside a matrix of hard styrene or acrylonitrile-styrene plastic. This compound microstructure is what gives HIPS and ABS favorable impact toughness and some minor flexibility.
The flexibility is important -- the stiffer a filament is, the more it will tend to warp while printing. Based on chemistry alone, I would expect styrene to be somewhat more prone to warping than ABS. And it would certainly be more brittle. So there doesn't seem to be much reason to use it as filament.
Interesting sidenote: PLA/PHA has very favorable mechanical properties because the PHA forms a very similar flexible microstructure inside the hard PLA matrix. PLA/PHA is good stuff because it mimics ABS and HIPS!